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Biomedical subjects

C Chung

Publications and source records attributed to C Chung.

At least 91 records · Page 5Linked to original sources
PubMed1988

Radiation does from medical in-vivo prompt gamma-ray activation using a mobile nuclear reactor.

A method of medical diagnosis of toxic elements, using a neutron beam from a mobile nuclear reactor to perform partial-body in-vivo prompt gamma-ray activation technique, has been developed. Both neutron and gamma-ray dose equivalents in an irradiated phantom and around medical researchers were measured and evaluated. Neutron flux at various kinetic energies was measured using an activation foil technique, and the neutron dose equivalents at tissues of risk inside the irradiated phantom were calculated by neutron transport code. Gamma-ray dose equivalents inside the irradiated phantom and around the nuclear reactor were measured by thermoluminescent dosimeters. The risk associated with the neutron and gamma radiation dose equivalents received by both the irradiated phantom and medical researchers were evaluated in detail. The radiation safety of the in-vivo medical diagnosis using the mobile nuclear reactor, under the context of radiation protection guidelines, is discussed.

Activation Analysis↗
PubMed1987

[3H]TCP binding sites in Alzheimer's disease.

Quantitative autoradiography was used to determine the density and distribution of [3H]1-[1-(2-thienyl)-cyclohexyl]piperidine ([3H]TCP) binding sites in human hippocampal tissue sections from control and Alzheimer's disease patients. Some Alzheimer's cases showed no changes in binding site density while other cases showed substantial declines in the CA1 region. [3H]TCP binding in the CA1 region from Alzheimer's patients was reduced an average of 40% while the other hippocampal regions were unaffected. It is proposed that the loss of [3H]TCP sites in the hippocampal CA1 region of certain Alzheimer's cases is associated with the greater cell loss observed in cases of severe Alzheimer's disease.

Alzheimer Disease↗
PubMed1985

A feasibility study of the in vivo prompt gamma activation analysis using a mobile nuclear reactor.

A facility for in vivo prompt gamma activation analysis using moderated neutron beams from a 0.1 W mobile nuclear reactor is described. The low-power nuclear reactor provides total neutron flux of 3.3 X 10(4)n cm-2 s-1 on the surface of a vertical beam tube to which a liquid phantom is positioned. The capability of such a partial-body irradiation facility is demonstrated by measuring trace amounts of toxic cadmium in kidney. The detection limit of Cd in kidney for a skin dose of 1.66 mSv (166 mrem) is 1.34 mg under 500 s irradiation. This facility therefore combines the advantages of mobility with high sensitivity of detection of a toxic element under low neutron and gamma doses.

Cadmium Poisoning↗
PubMed1984

In search of a status for acupuncture.

Acupuncture treatment is currently generating increased interest in various parts of the world. The effectiveness of this quasi-medical procedure, which has survived for almost 5 000 years, is considered on the strength of statistical data obtained at an institution where such treatment is applied under acceptable scientific circumstances. Explanations are sought for the encompassing extent of treatment claims and the continued support for this technique which is often subjected to severe criticism in modern contexts. The roles of literacy, tradition and convention, a placebo effect and psychological factors as explanatory agents are discussed. The procedure also has possible psychophysical and physiological foundations which sufficiently warrant further scientific effort to find an explanation for this phenomenon.

Acupuncture Therapy↗
PubMed1984

Comparison of central gastric antisecretory effects of desmethylimipramine, doxepin and pirenzepine in rats.

Certain tricyclic drugs, some of which are primarily used clinically as antidepressants, have been shown to act as gastric antisecretory agents. The anatomical site(s) and mechanism(s) of action of these agents is, however, in most cases unclear. In this study, we found that desmethylimipramine (DMI) was approximately 28 times more potent in inhibiting gastric acid secretion when administered intracerebroventricularly (i.c.) than when administered intravenously (i.v.) in pylorus-ligated rats, which is indicative of a site of action in the central nervous system. Qualitatively similar results were obtained with pirenzepine where the i.c./i.v. potency ratio was 8. Doxepin also preferentially inhibited acid secretion when given i.c. at low but not at high doses. Atropine and chlorpromazine were equipotent antisecretory agents by both routes of administration. Doxepin and DMI but not pirenzepine were effective inhibitors of brain stem norepinephrine uptake in vitro thus making this an unlikely common mechanism to explain the central actions of these compounds.

Animals↗
PubMed1984

Hematologic data of selenium-deficient and selenium-supplemented rats.

Effect of dietary selenium as sodium selenite on in vivo hematological parameters of Sprague-Dawley rats was examined over a 7-month period. Dietary selenium did not alter total hemoglobin, hematocrits, erythrocyte counts, or the osmotic fragility pattern of rat blood. Selenium-excessive (1.0 ppm) rats showed slightly lower but not significantly lower methemoglobin levels than selenium-adequate (0.1 ppm) or selenium-deficient rats. Platelet counts tended to be higher in selenium-excessive rats and lower in selenium-deficient rats than in selenium-adequate rats, but the differences were not statistically significant. No clear trends were observed regarding the effect of dietary selenium on total leukocyte and differential leukocyte counts. After 7 months of dietary treatment blood glutathione peroxidase activity in selenium-deficient rats and in selenium-excessive rats was 16.8% and 142.2% of the activity in selenium-adequate rats. The results indicate that long-term selenium deficiency in rats produces no abnormal hematological parameters or any compensated hemolytic anemia in vivo.

Animals↗
PubMed1983

Thymosin treatment: serum corticosterone and lymphocyte mitogenesis in moderately and severely protein-malnourished mice.

The present studies were performed to determine the levels of serum corticosterone (SC) and the proliferation of lymphocytes in response to phytohemagglutinin (PHA) in mice that were injected with thymosin fraction V and fed low protein diets. We found that protein-malnourished mice had consistently higher SC values than the control animals. This result confirms the existence of nutritional stress, which stimulates the adrenal glands increasing the release of corticosteroid hormones. No changes were observed in the SC level in controls whether or not thymosin was injected. However, in mice fed a protein-deficient diet, there was a significant decrease in SC levels after thymosin treatment, as compared to those of groups not treated with thymosin. Additionally, the thymosin effect on the SC levels was correlated with the cell-mediated immune changes. A significant increase in both PHA and lipopolysaccharide-induced lymphocyte transformation was observed in spleen cells from malnourished mice treated with thymosin fraction V. Thus, stress-induced glucocorticoid immunosuppression was demonstrated in malnourished mice. Our results suggest that components of thymosin fraction V may be involved in the mechanism of the restoration of lymphocyte transformation that was suppressed by glucocorticoid in protein-malnourished mice.

Adrenal Glands↗
PubMed1983

Studies on MK-208 (YM-11170) a new, slowly dissociable H2-receptor antagonist.

MK-208 [3-(((2-(aminoiminomethyl)amino)-4-thiazolyl)-methyl)thio)-N'-(a minosulfonyl) propanimidamide], also known as YM-11170, is a highly potent histamine H2-receptor antagonist in guinea-pig atria, acting via a unique binding mechanism. Unlike ranitidine, the onset of action of this compound was slow and its inhibitory action was difficult to remove from the tissues by repeated washing. Preincubation of atria with ranitidine, however, protected the H2-receptor from these prolonged inhibitory effects of MK-208. The H2-receptor antagonism produced by MK-208 was not surmountable by increasing concentrations of dimaprit. The compound did not alter the response of this tissue to isoproterenol or affect basal atrial rate under conditions where maximal H2-receptor blockade was achieved. In dogs, MK-208 was effective in inhibiting gastric acid secretion evoked by histamine, gastrin and 2-deoxy-D-glucose. Orally, it was approximately 7 times as potent as ranitidine against histamine-induced secretion, and its duration of action was substantially longer. The compound was also highly effective in inhibiting basal acid secretion in chronic gastric fistula rats.

Animals↗
PubMed1982

Fracture of the clavicle following radical neck dissection and postoperative radiotherapy: a case report and review of the literature.

The treatment of head and neck cancer with radiotherapy and radical neck dissection has many recognized complications. Radiotherapy in therapeutic doses can produce devascularization and weakening of bone. Radical neck dissection results in altered mechanics of the shoulder girdle and a disruption of normally balanced forces acting on the clavicle. An unusual case of clavicle fracture which is considered to have resulted from an interaction of the effects of these therapies is discussed. An approach for recognizing and distinguishing this entity by its time course, and radiographic and nuclide bone scan appearance is presented.

Adult↗